Chinese Takeout

Water watch for foreign invaders

By Margaret Tearman

They are coming by water, but you won’t catch them sailing up the Patuxent like the British in the War of 1812.
These invaders are a lot smaller but with the potential to pack a wallop on our shores.
You can help stop this enemy before all heck breaks loose.

Chinese Mittens Crabs

This small East Asian native invaded Europe before making its way across the pond. First found here in 1962 in the Great Lakes, the Chinese mitten crab has colonized the Gulf Coast, San Francisco Bay, the Hudson River and Chesapeake Bay.
Although small and unassuming, this crab is bad enough to earn a most wanted listing as Injurious Wildlife under the Federal Lacey Act, which makes it illegal to import, export or conduct interstate commerce with listed species without a permit.
The impact these crabs may have on local waters is unknown, but the discovery of egg-carrying females makes it likely that the crabs are making themselves at home.
To keep a tally on the crabs’ population and migration, researchers at the Smithsonian Environmental Research Center set up a Mitten Crab Hotline.
“We’ve had a lot of interest and calls to the hotline,” says spokeswoman Kristen Minogue. “But so far, no Chinese mitten crabs. All the crabs have been misidentified.”
With the distinct furry claws for which they are named, adult mitten crabs should be easy to identify. The other main identifying characteristics:
• Smooth, round, light-brown to olive-green carapace, three to four inches wide in adults.
• Furry white-tipped claws equal in size.
• U-shaped notch in the carapace between the crab’s eyes.
• Eight sharp-tipped walking legs but no swimming legs. Legs are over twice the length of the carapace.
Juveniles with a carapace less than one inch may not have hair on their claws; those over one inch will have hair.
If you do catch a mitten crab, don’t throw it back alive. Note the precise location where the animal was found. If you can, take a close-up photo and then freeze the crab, keep it on ice or, as a last resort, preserve it in rubbing alcohol.
Then call the Mitten Crab Hotline at 443-482-2222 for further instructions on what to do with your (un)lucky catch.

Northern Snakehead

Another Asian invader turned up last week on the Rhode River. A northern snakehead swam right into the net of researchers and student summer interns from the Smithsonian Environmental Research Center.
The discovery was the first reported in local waters. The first northern snakehead in Maryland was caught in 2002 in a Crofton pond. Amid much media attention, the Crofton snakehead population was eradicated. But in 2004, the fish appeared in the Potomac River.
Because the snakehead prefers freshwater, scientists hoped the higher salinity at the mouth of the Potomac would keep the fish from venturing farther. But after this year’s heavy spring rains, Chesapeake tributaries are at some of their lowest salinity levels in 30 years, giving the snakehead a comfy swim — or walk — out of the Potomac into the Chesapeake and onward.
The northern snakehead is a creepy fish; it can survive up to four days out of water if it stays moist. Snakeheads are voracious predators, able to eat other fish and animals up to one-third of their own body size. It is this appetite scientists fear, putting native species at risk and causing changes to the natural food chain.
Natural resource people take this threat seriously. Possession of a live northern snakehead is a violation of state law. If you catch one, do not release it. Kill it and call the Maryland Department of Natural Resources toll-free at 1-877-520-8DNR x8230.